ZyXEL Communications ZYWALL10 - Manual (Page 253)

ZyWALL 10 Internet Security Gateway
Glossary of Terms O
Cookie A string of characters saved by a web browser on the user's hard disk. Many web pages
send cookies to track specific user information. Cookies can be used to retain
information as the user browses a web site. For example, cookies are used to
'remember' the items a shopper may have in a shopping cart.
Countermeasures Techniques, programs, or other tools that can protect your computer against threats.
Cracker Another term for hackers. Generally, the term cracker refers specifically to a person who
maliciously attempts to break encryption, software locks, or network security.
Cracker Tools Programs used to break into computers. Cracker tools are widely
distributed on the Internet. They include password crackers, Trojans, viruses, war-
dialers, and worms.
Cracking The act of breaking into computers or cracking encryption.
Crossover
Ethernet cable
A cable that wires a pin to its opposite pin, for example, RX+ is wired to TX+. This cable
connects two similar devices, for example, two data terminal equipment (DTE) or data
communications equipment (DCE) devices.
Cryptoanalysis The act of analyzing (or breaking into) secure documents or systems that are protected
with encryption.
CSU/DSU
Channel Service Unit/Data Service Unit. CSUs (channel service units) and DSUs (data
service units) are actually two separate devices, but they are used in conjunction and
often combined into the same box. The devices are part of the hardware you need to
connect computer equipment to digital transmission lines. The Channel Service Unit
device connects with the digital communication line and provides a termination for the
digital signal. The Data Service Unit device, sometimes called a digital service unit, is
the hardware component you need to transmit digital data over the hardware channel.
The device converts signals from bridges, routers, and multiplexors into the bipolar
digital signals used by the digital lines. Multiplexors mix voice signals and data on the
same line.
DCE
Data Communications Equipment is typically a modem or other type of communication
device. The DCE sits between the DTE (data terminal equipment) and a transmission
circuit such as a phone line.
Decryption The act of restoring an encrypted file to its original state.
Denial of Service Act of preventing customers, users, clients or other machines from
accessing data on a computer. This is usually accomplished by interrupting or
overwhelming the computer with bad or excessive information requests.
DHCP
Dynamic Host Configuration Protocol automatically assigns IP addresses to clients
when they log on. DHCP centralizes IP address management on central computers that
run the DHCP server program. DHCP leases addresses for a period of time, which
means that addresses are made available to assign to other systems.